Reproductive biology of Octopus tehuelchus d’Orbigny, 1834 (Cephalopoda: Octopodidae) in southern Brazil

Abstract

Octopus tehuelchus is a small octopus endemic to subtropical and temperate waters of the southwestern Atlantic continental shelf. Its reproductive biology was studied by examining 319 individuals, measuring 20 to 79 mm mantle length (ML), collected between 1979 and 2009 along the coast of southern Brazil. Females are more numerous in shallower waters and attain larger size than males. Fully mature males and females were observed in all seasons and mean mantle length at maturity was 46 mm for females and 27 mm for males. The number of intraovaric oocytes of maturing females ranged from 20 to 448 and was positively correlated with female size. In mature females, a wide range of intraovaric oocytes diameters was observed, in some cases with a bimodal distribution. The number of eggs in the four layings ranged from 86 to 237, the diameters ranged from 8.2 to 14.5 mm and no bimodality was observed. Digestive gland grew proportionally to body weight along maturation in females but not in males, suggesting accumulation of reserves for spawning and parental care in females and priority for sexual maturation over growth in males. The comparison of the reproductive cycle of O. tehuelchus in southern Brazil with populations from northern Patagonia shows that the species has the potential for year round spawning, but ecological constrains only allows it to express this potential in the lower latitudes of its distribution.